1. Field of the Invention
The present invention relates to a connection reservation control system for use with information communications networks such as ATM switching system networks which permit permanent virtual connections to be set up using virtual connection units.
2. Description of the Related Art
An ATM (Asynchronous Transfer Mode) switching system network (hereinafter referred to as a network domain) is a network in which plurality of ATM switching systems (hereinafter referred to as network elements (NEs)) are connected by physical line interfaces. An ATM network management system (hereinafter referred to as NMS: Network Management System) is a system that has the functions of resource management, connection management, failure (alarm) management, security management, traffic management, etc., for the purpose of managing an ATM switching system network, in particular.
As a unit for connecting each NE or line organically in a network domain, a primitive virtual connection unit, such as a VP (Virtual Path) or a VC (Virtual Channel), is known.
As shown in FIG. 1, the VP or VC is defined as allocated to a physical link that connects together network interfaces (User Network Interfaces (UNI)/Network Network Interfaces (NNI)) of the respective NEs, thereby reserving a Permanent Virtual Channel (PVC) connection which is an end-to-end permanent virtual connection.
The PVC connection occupies a portion of the fixed bandwidth of a line interface all the time. To permit efficient utilization of the line interface, therefore, the demand for implementing a reservation controlling function on PVC connections has been increasing. If the bandwidth occupancy varies widely from hour to hour or from day to day, then there will arise a need for such a type of connection management as distributing connections according to the varying occupancy changes from hour to hour or from day to day.
These facts mean that the reservation controlling function of switching PVC connections from hour to hour is closely linked with the connection management function for the PVC connection. Thus, how to link the two network functions with each other for efficient utilization of lines will be an important problem to be solved by the ATM network management system.
Information communications networks, particularly ATM switching system networks, are now in the process of standardization by many international network organizations such as TMN, OSI, etc., or NE vendors. Thus, the ATM network management system is employed by each network organization or NE vendor. An important problem that confronts ATM network system operators is how to maintain a balance between a reduction of the cost of installation of facilities to make up a network and the reservation of the line bandwidth for PVC connections that customers use. From this point of view as well, an ATM network management system has been demanded in which the PVC connection reservation controlling function and the connection management function of the PVC connection are combined with each other organically.
As an ATM network management system, a product having the functions of resource management, connection management, failure (alarm) management, security management, and traffic management within a network domain is known conventionally. The function of setting up an end-to-end PVC connection between each NE has already been put to practical use as a portion of a conventional connection management function.
Moreover, a PVC connection reservation controlling function has already been put to practical use which is arranged such that NEs each include a command file necessary to set up PVC connections, and a set of commands described in the command files is activated at a specified time.
Furthermore, in STM (Synchronous Transfer Mode) switching system networks which are conventional general line switching networks, a reservation controlling function has been implemented which generates or removes a private line at a specified time.
For a network domain composed of a plurality of ATM switching systems, end-to-end PVC connection setup and reservation controlling function requirements have been recognized. However, the fact is that no specific techniques or system products for implementing the function exist.
That is, the conventional ATM network management systems have no connection reservation controlling function linked with the PVC connection setup and cannot flexibly meet a request to switch PVC connections from hour to hour and a situation requiring transmission of a large number of cells at regular intervals.
Thus, with the conventional systems, it is required to set up an end-to-end PVC connection between each NE. The connection setup involves setting many parameters such as a route, a quality level, etc., which increases the possibility that human errors may creep in.
On the other hand, in the conventional system in which a command file is set up for each NE and a set of commands described in the command files is activated at a specified time, there is the possibility that a mismatch may occur among data on a location to which a connection is to be made, which are placed in the command files of the respective NEs to set up one PVC connection. The occurrence of a mismatch will result in failure to set up that PVC connection normally.